The ribosome, as the organelle essential for protein synthesis, plays a key role in cell growth and its regulation. We have been studying the structure and function of bacterial ribosomes, as well as the mechanism of their assembly, both in vitro and in vivo. Specifically, our recently effort has focussed on the identification of genes for ribosomal proteins and rRNA, and studies of the expression of these important genes and the identification of other genes involved in regulating their expression. Our recent success in isolation of DNA carrying many r-protein genes or rRNA genes as transducing phage DNA or small plasmid DNA has provided a new way to identify and map r-protein genes (as well as other genes required for their expression) and to study the regulation of their expression. We have already obtained much information on these important ribosomal genes by applying to our systems several newly developed powerful technologies such as heteroduplex analysis, specific dissection of isolated ribosomal operons by various restriction enzymes, cloning of such DNA fragments into plasmids and vector phages, and in vitro synthesis of r-proteins using various DNA fragments. We will continue these approaches to complete mapping of isolated ribosomal genes and elucidate their genetic organization. Bacterial ribosomes contain 3 different RNA molecules and some 50 to 55 different protein components. We wish to understand the complex series of events which originate in the transcription of the more thlan 60 genes and culminate in the formation of the complex, yet specific, structure of the organelle. More specifically, we wish to identify (hopefully all) the genes coding for ribosomal components and study their genetic organization and the control of their expression. In addition, we wish to learn how synthesis of ribosomal RNA and r-proteins is coordinated and how ribosome assembly takes place from these components in a controlled way in vivo. Eventually, we would like to reproduce all the in vivo assembly events in the test tube and to study in vitro, factors regulating the organelle biogenesi.